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 Post subject: CPU Frequency scaling on N230 (Atom N450)
PostPosted: 27/07/2011, 11:07 
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Joined: 02/01/2011, 23:55
Posts: 8
My Samsung N230 is working great under Ubuntu 11.04 . Only problem: battery life sucks compared to W7. There is a well documented power regression in the linux kernel starting with 2.6.38, and some workarounds available. I've applied them all, somehow improving the problem. Now I can get 3 hours if I judiciously use brightness.

However, while trying to tinker with other things, I realized that the CPU frequency scaling is maybe off. This is the outuput of cpufreq-info

Code:
miccoli@netbook-N230:~$ cpufreq-info
cpufrequtils 007: cpufreq-info (C) Dominik Brodowski 2004-2009
Report errors and bugs to cpufreq@vger.kernel.org, please.
analyzing CPU 0:
  driver: acpi-cpufreq
  CPUs which run at the same hardware frequency: 0 1
  CPUs which need to have their frequency coordinated by software: 0
  maximum transition latency: 10.0 us.
  hardware limits: 1000 MHz - 1.67 GHz
  available frequency steps: 1.67 GHz, 1.33 GHz, 1000 MHz
  available cpufreq governors: conservative, ondemand, userspace, powersave, performance
  current policy: frequency should be within 1000 MHz and 1.67 GHz.
                  The governor "ondemand" may decide which speed to use
                  within this range.
  current CPU frequency is 1.67 GHz.
  cpufreq stats: 1.67 GHz:31.57%, 1.33 GHz:4.11%, 1000 MHz:64.32%  (67378)
analyzing CPU 1:
  driver: acpi-cpufreq
  CPUs which run at the same hardware frequency: 0 1
  CPUs which need to have their frequency coordinated by software: 1
  maximum transition latency: 10.0 us.
  hardware limits: 1000 MHz - 1.67 GHz
  available frequency steps: 1.67 GHz, 1.33 GHz, 1000 MHz
  available cpufreq governors: conservative, ondemand, userspace, powersave, performance
  current policy: frequency should be within 1000 MHz and 1.67 GHz.
                  The governor "ondemand" may decide which speed to use
                  within this range.
  current CPU frequency is 1000 MHz.
  cpufreq stats: 1.67 GHz:30.13%, 1.33 GHz:3.99%, 1000 MHz:65.89%  (70145)


The frequency steps are only 1.67, 1.33 and 1 GHz. I thought that for the Atom n450 there was another frequency step at 800MHz. If the lowest frequency step should actually be there, then how can fix it? I believe adding this frequency step could sensibly improve my battery life.

I've been doing some googling but didn't find more info, however some other people report the same question about the frequency scaling of the atom n450 under linux missing the 800MHz

Even if you have no suggestions, can you please post the output of cpufreq-info if you have an atom n450 processor? just to check whether there are differences.

thanks, M

P.S. in case someone needs the information, the BIOS version is 01MA


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 Post subject: Re: CPU Frequency scaling on N230 (Atom N450)
PostPosted: 27/07/2011, 12:22 
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Joined: 02/01/2011, 23:55
Posts: 8
In case it helps, this is the output of powertop:

Code:
miccoli@netbook-N230:~$ sudo powertop -d
PowerTOP 1.13   (C) 2007 - 2010 Intel Corporation

Collecting data for 15 seconds


Your CPU supports the following C-states : C1 C2 C4
Your BIOS reports the following C-states : C1 C2 C4
Cn             Avg residency
C0 (cpu running)        (20.1%)
polling        0.2ms ( 0.0%)
C1 mwait     0.2ms ( 0.5%)
C2 mwait     0.7ms (10.4%)
C4 mwait     2.6ms (69.0%)
P-states (frequencies)
  1.67 Ghz    25.8%
  1333 Mhz     1.5%
  1000 Mhz    72.7%
Disk accesses:
The application 'flush-8:0' is writing to file 'Visited Links' on /dev/sda7
Wakeups-from-idle per second : 443.9   interval: 15.0s
Power usage (ACPI estimate): 8.8W (0.8 hours)
Top causes for wakeups:
  17.3% ( 76.4)   kworker/0:0
  16.0% ( 70.5)   [kernel scheduler] Load balancing tick
  15.3% ( 67.5)   [extra timer interrupt]
   9.9% ( 43.8)   compiz
   9.0% ( 39.7)   LCDd
   6.9% ( 30.3)   chrome
   4.0% ( 17.9)   [Rescheduling interrupts] <kernel IPI>
   3.9% ( 17.1)   SignalSender
   3.8% ( 16.6)   opera
   2.9% ( 12.6)   [uhci_hcd:usb5, brcm80211] <interrupt>
   2.3% ( 10.0)   xbindkeys
   2.3% ( 10.0)   nautilus
   1.5% (  6.7)   [TLB shootdowns] <kernel IPI>
   1.5% (  6.6)   [ahci] <interrupt>
   1.1% (  5.0)   syndaemon
   0.0% (  0.0)D  flush-8:0
   0.4% (  1.9)   gnome-terminal
   0.3% (  1.3)   [kernel core] hrtimer_start (tick_sched_timer)
   0.3% (  1.3)   [Function call interrupts] <kernel IPI>
   0.2% (  1.0)   [kernel core] add_timer (wl_timer)
   0.2% (  1.0)   kworker/u:5
   0.2% (  0.9)   dropbox
   0.2% (  0.7)   unity-panel-ser
   0.1% (  0.5)   indicator-sysmo
   0.1% (  0.3)   unity-applicati
   0.1% (  0.3)   rtkit-daemon
   0.0% (  0.2)   NetworkManager
   0.0% (  0.2)   gnome-settings-
   0.0% (  0.2)   update-notifier
   0.0% (  0.1)   [i915] <interrupt>
   0.0% (  0.1)   wpa_supplicant
   0.0% (  0.1)   irqbalance
   0.0% (  0.1)   ssh-agent
   0.0% (  0.1)   [kernel core] inet_twdr_hangman (inet_twdr_hangman)
   0.0% (  0.1)   [kernel core] laptop_io_completion (laptop_mode_timer_fn)
   0.0% (  0.1)   [kernel core] sk_reset_timer (tcp_delack_timer)
   0.0% (  0.1)   gconfd-2
   0.0% (  0.1)   cron
   0.0% (  0.1)   Xorg
   0.0% (  0.1)   gnome-power-man


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